Abstract
The occurrence of biotypes of pest insects virulent to resistant crop varieties is a serious problem for the utilization of resistant crops; therefore, it is important to prevent the occurrence of resistance-breaking biotypes by examining their characteristics. In this paper, the development and reproduction of three biotypes of the green rice leafhopper Nephotettix cincticeps (Uhler) were examined on resistant rice varieties of Chugoku 105 (carrying the resistance gene Grh1), Saikai 182 (Grh2), and Aichi 80 (Grh3(t)). Biotypes 1, 2, and 3 exhibited a high survival rate, short developmental period, long adult longevity and high fecundity on the respective Grh1, Grh2, and Grh3(t)-carrying resistant varieties to which they are virulent. The total sugar content of the honeydew excreted by these biotypes was high, suggesting that each biotype has the ability to suck phloem sap from the resistant variety to which it is virulent. The nymph survivorship and development, adult longevity, fecundity, and total sugar content of honeydew excreted by the three biotypes were similar to those observed in the non-selected line of the Nipponbare variety carrying no resistance gene. These results indicate no fitness difference in development and reproduction between the three biotypes and the non-selected line of N. cincticeps on susceptible rice varieties.
